GB2340994A

GB2340994A - Optoelectronic integrated circuit

Info

Publication number: GB2340994A
Application number: GB9818618A
Authority: GB
Inventors: William Eric Corr
Original assignee: LSI Logic Corp
Current assignee: LSI Corp
Priority date: 1998-08-26
Filing date: 1998-08-26
Publication date: 2000-03-01
Also published as: GB9818618D0

Abstract

An integrated circuit is described for receiving parallel frequency division multiplexed optical input signals through a multi-mode optical fibre. The integrated circuit includes an input port (18), and a prism device (22) for splitting the optical input into its different spectral components. Light shielding walls (26) guide the optical components to respective photosensitive regions (16) of the die (12) to provide direct on-chip parallel optical input signals without the need for an external optical decoder.

Description

2340994 OPTICAL/ELECTRONIC WITGRATED CERCUJIT This invention relates to an

integrated circuit of the type having at least one optical input. In one aspect, the invention relates to receiving an optical signal representing a plurality of signals in parallel, for example, a parallel datastream.

As used herein, the term "optical" is not limited to visible light, but is intended to cover other types of radiation which obey substantially the laws of optics, including, fo r example, infra-red light and ultra- violet light.

The invention is also usable with the type of integrated circuit die described in copending U.K. patent application No- 9712177.6 entitled "Low Skew Signal Distribution of Integrated Circuits" which describes an integrated circuit die which is clocked by an o-'T chip source.

The optical transmission of signals can offer advantages in terms of speed of distribution, and reduction of signal skew. This is extremely important for high speed integrated circuits, and for systems employing a plurality of integrated circuits.

It would be desirable to provide an integrated circuit which is able directly to receive an optical signal representing parallel signals.

In one aspect, the invention provides an integrated circuit compfising a D I semiconductor die having a plurality of photosensitive areas, an optical input for receiving an external optical signal, and optical means for splitting the optical signal into component signals and for illuminating one or more photosensitive areas with a respective opt.cal component of the input signal.

The optical means may comprise any suitable device for splitting the incoming fight. For example, the optical means may comprise a prism for diffracting incorning light into spectral components. Alternatively, the optical means could comprise a polariser for splitting incoming light according to its polarization.

Preferably, the optical means comprises one or more guides for defining channels for directing the light components to the respective photosensitive areas of the integrated circuit.

2 With the invention, incoming light can be divided into its component parts and each signal component can be provided to a respective photosensitive region of the semiconductor die. The invention permits parallel signal to be received as a combined optical signal directly into an integrated circuit package. The optical signal is divided to form a plurality of direct on-chip optical signals without the need for an external decoder.

The optical input means may comprise a simple window for receiving light from an external source. Preferably, the optical input means comprises a port, for example, an optical fibre connector, for receiving light fi7om an optical fibre.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings, in which- Fig. I is a schematic plan view of an integrated circuit; and Fig. 2 is a schematic perspective view illustrating the optical means of the device in detail.

Referring to the drawings, an integrated circuit device 10 comprises a package 12 in which is received a semiconductor die 14. The device 10 may include the conventional wire bonded connections to connecting pins or connecting pads of the device, but these are not shown in the drawings for the sake of brevity.

The semiconductor die 14 includes a plurality of photosensitive regions 16 responsive to received light. The regions 16 represent optical sensors for receiving optical signals, as described below. The regions 16 may be coupled to conditioning circuitry (for example, an amplifier and threshold circuit) as described in the above referenced GB 9712177.6, for converting the optical signals into discrete digital signals. In this embodiment, the photosensitive regions 16 generally have the same response to incident light. In other words, the photosensitive regions are not capable of discriminating one component of an optical signal from another component.

The device 10 comprises an optical input in the form of a connector 18 for coupling to the end of an optical fibre 20, for receiving optical signals therefrom. In this embodiment, the fibre 20 is a multi-mode optical fibre for carrying a plurality of parallel optical signals represented by different light frequencies (frequency division multiplexing).

3 integrally coupled to the connector 18 is an optical device in the form of a microprism 22 for splitting the incoming light into its spectral components. The spectral components exit the face 24 of the micro-prism at a position and angle depending on the frequency band of the light signal component.

A plurality of light shielding walls 26 extend from the output face 24 of the microprism 22 to define channels for guiding the output frequency components to respective photo-sensitive regions 16 of the die 12. The walls 26 prevent optical cross-talk between the different frequency components downstream of the micro-prism. Translucent material (depicted schematically at 28) is placed within each light "channel" so that the light can be diffracted to illuminate the respective photosensitive region 16, without precise focusing or line-of-sight alignment being required.

In the present embodiment, one of the light band components can be used as a clock signal to operate synchronous elements on the die 12, as described in the above referenced GB 9712177.6. In that case, an additional light shield '30 would be provide A light path for the optical clock signal to a plurality of different clock photosensitive areas 3 2 of the die 12 at different positions across the surface of the die. The shield _3) 0 prevents interference between the optical clock and the other optical bands as the signals are guided over the surface of the die 12.

The clock signal could be used as a data-extraction clock for extracting information from other frequency bands received through the optical fibre. The parallel optical signals may additionally or alternatively include one or more control signals.

In this embodiment, the die is based on a silicon substrate (MOS), but other embodiments may used different semiconductor materials. Most semiconductor substrates exhibit photo-sensitivity, which can enable simple implementation of the photo-sensitive areas 16.

It will be appreciated that the foregoing description is merely illustrative of a preferred embodiment of the invention, and that many modifications may be made within the scope of the invention. Features to be of particular importance are defined in the appended claims. However, the Applicant claims protection for any novel feature or idea

4 described herein and/or illustrated in the drawings whether or not emphasis has been placed thereon.

Claims

1. An integrated circuit comprising a sen-dconductor die having a plurality of photosensitive areas, an optical input for receiving an external optical signal, and optical means for splitting the optical signal into component signals and for illuminating one or more photosensitive areas with a respective optical component of the input signal.

2. An integrated circuit according to claim 1, wherein the optical means comprise means for splitting the light into spectral components.

3. An integrated circuit according to claim 2, wherein the optical means omprises a prism.

4. An integrated circuit according to claim 3, wherein the prism is a micro-prism.

5. An integrated circuit according to claim 1, 2, 3 or 4, wherein the optical means comprises a polariser.

6. An integrated circuit according to any preceding claim, further comprising means 1 for guiding the component signals to illuminate a respective photosensitive area of the semiconductor die.

7. An integrated circuit according to claim 6, wherein the guiding means compri,e means defining a plurality of discrete light channels.

8. An integrated circuit according to claim 6, wherein the guiding means comprise one or more light shielding walls.

9. An integrated circuit, wherein each light channel includes translucent material.

6

10. An integrated circuit according to any preceding claim, wherein the optical input means comprises means for receiving an optical fibre.

11. An integrated circuit according to any preceding claim, wherein at least one of the photosensitive areas comprises an optical input to a data input of the die.

12. An integrated circuit according to any preceding claim, wherein at least one of the photosensitive areas comprises an optical input to a clock input of the die.

13. An integrated circuit according to claim 12, comprising a plurality of photosensitive regions for receiving a common optical clock signal.

14. An integrated circuit according to any preceding claim, wherein at least one of the photosensitive areas comprises an optical input to a control input of the die.

15. An assembly comprising an integrated circuit as defined in any preceding claim, 0 and an optical fibre coupled thereto for delivering parallel optical input signals to the integrated circuit.

16. An assembly according to claim 15, wherein the fibre is a multi-mode optical fibre.